My personal opinion is that anyone should stay away from Livonah when possible. She's completely outclassed by Dark Squire Ruby and even more so by Ria.

But that's my opinion, I know a lot of people like her low Cost, high ATK thing and are willing to take the risk of Livonah snatching defeat from the jaws of victory (courtesy to Eclipse for coming up with that one lol).

You should try not to use Livonah unless you have a group that has very low combo levels. However, if you have low combo levels, your other abilities will not activate easily either so unless you are extremely confident that you can beat your opponent, stay away from Livonah.